What was found
AIRCRAFT WAS GROUNDED. RT ENGINE HAS LONG PERIODS OF N1 AND N2 FUEL FLOW FLUCTUATIONS AT FL390/.78M N1 RANGE 91.4 TO 95.0, FUEL FLOW RANGE 2.5 TO 3.1, THROTTLES SPLIT WITH AUTOTHROTTLE ON, CHANGED ALTITUDE TO FL330 WITH NO IMPROVEMENT. AT IDLE, AUTOTHROTTLE DISENGAGED AND RT ENGINE HAD SMALL POWER SURGE. REPLACED RT ELECTRONIC ENGINE CONTROLLER, IAW SIC 08L40073002, THRUST LEVER ANGLE RESOLVER (AALA202011259001), IAW AMM 76-11-05, AND RT T12 SENSOR (AALA202011259010), IAW AMM 73-21-05. OPERATIONS CHECK GOOD.